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Derivative Financial Instruments Gains and Losses (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2018 | Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative settlement (gain) loss | $ 24,528 | $ (7)
Net derivative (gain) loss | 7,529 | (114,774)
Oil Contracts [Member] |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative settlement (gain) loss | 20,748 | 9,084
Net derivative (gain) loss | 13,966 | (49,590)
Gas Contracts [Member] |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative settlement (gain) loss | (6,410) | (17,506)
Net derivative (gain) loss | 9,990 | (44,468)
NGL Contracts [Member] |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Derivative settlement (gain) loss | 10,190 | 8,415
Net derivative (gain) loss | $ (16,427) | $ (20,716)

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- Definition Realized gain or loss recognized in earnings from the settlement of derivative instruments not designated as hedges. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959 + Details
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